Generic admin area: an admin layout built on the shared AppShell from @frigear-nu/ui with a grouped sidebar (the
admin.nav menu: Overview, Manage and Settings, see ADMIN_NAV_GROUPS), a ⌘K palette over the same entries, a
back-to-site link and the account menu in the sidebar footer. The navbar shows a muted area › section eyebrow, not a
title: every page renders the one <h1> through PageHeading. The area also has a guarded dashboard (the admin.dashboard widget areas). Other modules register their admin
pages, nav entries and widgets into it. Pages are built from the @frigear-nu/ui page patterns (PageHeading,
SectionCard, TableCard, …).